21400434 has 48 divisors (see below), whose sum is σ = 52341120. Its totient is φ = 6259680.

The previous prime is 21400429. The next prime is 21400451. The reversal of 21400434 is 43400412.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3879 + ... + 7605.

It is an arithmetic number, because the mean of its divisors is an integer number (1090440).

Almost surely, 2^21400434 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21400434, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26170560).

21400434 is an abundant number, since it is smaller than the sum of its proper divisors (30940686).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21400434 is a wasteful number, since it uses less digits than its factorization.

21400434 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3775 (or 3772 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21400434 is about 4626.0603108909. The cubic root of 21400434 is about 277.6349866763.

Adding to 21400434 its reverse (43400412), we get a palindrome (64800846).

The spelling of 21400434 in words is "twenty-one million, four hundred thousand, four hundred thirty-four".